1. Field of the Invention
This invention relates to numerically controlled mills or lathes, and more specifically to such mills or lathes being interfaced to and controlled by computers.
2. Description of the Prior Art
Numerically Controlled (NC) machines are available in the market in numerous forms, such as; milling machines, lathes, lathe-o-mills, swiss lathes etc. Most of these machines are designed for the production environment and are not available to the home user primarily because of the relatively high cost. The cost is attributed to the expensive components used to provide the two or more computer-controlled axes of motion. Each axis of a multi-axis computer controlled milling machine requires one motor, one motor controller, one signal feedback encoder and possibly one power supply. In order to produce an arbitrary 3-D shape, all three axes of movement are usually computer controlled.
Additionally, a special interface card together with the appropriate software controls these axes, together with the appropriate software running in the computer. In order to find a market for these machines with the average home user the cost must be brought down.
The PC-controllable material removal machine according to the present invention is similar in concept to a wood turning machine. One significant difference is that the cutting tool is milling (rotating) instead of being stationary. Further, of the generally used three axes of movement of the tool relative the work-piece to enable a three-dimensional shaping of the work-piece, only one axis is computer controlled (single axis material shaping machine). Movement of the workpiece relative the tool in the further two axes of movement is provided by manual or other means, and the correct tool path is calculated by the computer software by using prediction algorithms. Feedback of the position of the cutting tool relative the work-piece is by various sensors, for example linear or rotational and absolute or relative encoders.
In the invention, a material shaping machine has a frame, a work-piece holder and a tool holder for rotatably holding a tool. A computer performs real-time tool path claculations, based upon stored mathematical representations of a desired work-piece surface and stored mathematical representations of an actual tool geometry, by calculating a desired position of a tool cutting edge relative a measured position of the tool cutting edge and a measured position of the work-piece, and adjusting a distance between the desired tool cutting edge and the measured position of the tool cutting edge in a first direction, so that the tool cutting edge reaches the desired position.
The machine further advantageously has manipulation means for providing a relative movement of the work-piece and the tool cutting surface in a second direction and a third direction. The manipulation means are operated outside the computer control.
The machine preferably has sensors to determine the position of the work-piece relative the cutting surface of the tool and to send the position data to the computer.
The computer software preferably calculates a mathematical representation of the desired shape of the work-piece surface after machining, and uses the representation together with stored information regarding the shape of the tool and the cutting surface of the tool to control the relative distance between the tool cutting surface and the workpiece.
The representation is advantageously either an algebraic formula or a parametric formula.
In one embodiment of the machine, the tool holder is slidable relative the work-piece holder and the frame, to provide movement in the first direction.
The machine preferably has reciprocating means for selectively moving the tool holder in the first direction, the reciprocating means being controlled by software running on the computer; and where the reciprocating means is controlled by the computer software to move the tool holder corresponding to any detected movement of the workpiece by the manipulation means.
The work-piece is either rotatably held in the work-piece holder, to provide the second direction of movement of the work-piece, or is slidably held in the work-piece holder, to provide the second direction of movement of the work-piece. The first direction, the third direction and a rotation axis of the direction are generally perpendicular to each other. Alternatively, the first direction, the second direction and the third direction are generally perpendicular to each other.
In a further embodiment of the machine, the work-piece is slidably held in the work-piece holder to provide the first direction of movement of the work-piece.
The machine preferably has reciprocating means for selectively moving the work-piece holder in the first direction, the reciprocating means being controlled by software running on the computer; and where the reciprocating means is controlled by the computer software to move the work-piece holder corresponding to any detected movement of the workpiece by the manipulation means.
The work-piece is either rotatably held in the work-piece holder, to provide the second direction of movement of the work-piece, or is slidably held in the work-piece holder, to provide the second direction of movement of the work-piece.
The first direction, the third direction and a rotation axis of the second direction are generally perpendicular to each other. Alternatively, the first direction, the second direction and the third direction are generally perpendicular to other.